Grenade

The grenade is a hand-held, thrown explosive weapon in Doom 3. "The infantry issue fragmentation grenade is activated by a twist detonator. Fire delay is 3 seconds, with an injury radius of 30 meters."

- PDA description

Combat analysis
The grenade is an explosive weapon, dealing splash damage. Grenades can bounce off walls but will explode on contact with a monster. They can be used in corridors to kill zombies around corners or behind cover. Do not use the grenade at close range, as the explosion can hurt the player. Also, do not cook the grenade for too long, or it will explode in the player's hand, killing him.

Tactical analysis
Grenades are useful for flushing out Z-Secs and chaingun commandos who have taken cover. The grenades can be thrown so that they will explode close to the concealed enemy, preferably while remaining hidden from their return fire. They can also be thrown directly at enemies in the open, and a single grenade can kill an imp, vulgar, or tentacle commando (although vulgars and tentacle commandos might occasionally survive, and would then require a few shots from a different weapon to finish them off). In all cases, the player should stay clear of the explosion to avoid taking splash damage. A grenade can kill multiple zombies with one explosion. Slow-moving enemies such as mancubi are inviting targets. They can also be used to quickly kill swarms of trites and ticks. Grenades are arguably the best way to dispatch the riot shield Z-Sec - if a grenade is thrown towards him at a low angle so that it bounces along the floor and hits his feet, the shield will not protect him from the blast.

Though grenades can be tough to aim for the inexperienced, they are not too difficult to aim properly once the player is accustomed to their mechanics. The longer the grenade is cooked, the further it can be thrown, and the sooner it will explode afterward. Quickly releasing the fire button and aiming at the ground will allow rolling the grenade across the ground, while a long cook time and a high angle is best for throwing the grenade over cover to hit Z-Secs. Although difficult to pull off at times, a mid-angle bounce against a wall is also possible, to hit monsters behind cover on the opposite side of the wall.

Trivia

 * This weapon has two names in the game: the name of the weapon itself is grenades, but the name of the ammo (which is the weapon itself) is hand grenades.